The present invention relates to a lock, particularly a mechanical lock. Mechanical locks that can be applied to doors, windows, shutters, and the like are known.
A mechanical lock of a known type has a fixed part suitable to house the lock mechanisms, and a movable part provided with a keyhole for the insertion of the key. The movable part, actuating the opening/closing mechanism of the lock, is typically locked by pins that are removed upon the insertion of the right key, thus allowing the movable part rotation.
For example, in a drum lock of a known type, the fixed part, or stator (starting from the inner surface) and the movable part or rotor (starting from the outer surface) are provided with respective radial cavities that are mutually alignable so as to define a seat within which they can radially translate a pin and a counter-pin. A spring is located between each pin and the stator, suitable to push the pin and the counter-pin in a radial direction from the outside inwardly. In the case that the key is not inserted, each pin, by virtue of the action of the respective spring, is within the respective radial cavity in such a position as to inhibit the rotor rotation within the stator. In the case that the key is inserted, the key profile allows moving within the respective radial cavity, from the inside outwardly, each pin and counter-pin so that the lower part of the pin and the upper part of the counter-pin are aligned with the outer edge of the rotor. In such a case, by rotating the key, the rotor is in turn able to rotate within the stator and actuate the lock opening/closing mechanism.
In terms of security, the mechanical lock of the prior art described above can be subjected to several breaking open operations.
For example, it is possible to destruct the rotor containing the counter-pins. Following the forced removal of the pins from the stator, the rotor can freely rotate with respect to the stator and actuate the lock opening/closing mechanism.
According to another breaking open operation, it is possible to apply a torsional tension onto the rotor, so as to cause the possible forced inclination of pins and counter-pins, due to the mechanical tolerances that are present between rotor and pins/counter-pins and between pins/counter-pins and stator. Subsequently, by lifting the counter-pins and the pins one by one, each of them moves outside the respective radial cavity and it is not able to come back to the initial position, since the rotor, which is subjected to the torsional tension, is rotated with respect to the stator. Once all the counter-pins and the pins are made to fall off of the rotor and the stator, the same rotor may freely rotate within the stator by actuating the lock opening/closing mechanism.
The latter breaking open operation can be successfully applied to other mechanical locks. In fact, it is sufficient to create a torsional tension between the fixed part (stator) and the movable part (rotor) to exploit those construction mechanical tolerances of the lock that are present also after the assembling of the same lock, in order to make the elements (pins, counter-pins, optionally, springs) used for actuating the lock opening/closing mechanism fall off from the radial cavities.
Furthermore, in the case of a hierarchic key system, i.e., multiple user keys, each of which being suitable to open only one lock, and a master key or passepartout suitable to open all the locks, the mechanical lock of the prior art described above may easily allow a burglar, who has a user key available, retrieving even the master key code.
In fact, a user key being available, it is possible to file a master key until reproducing all the components of the user key code, with the exception of one. The part of the master key that has not been filed is progressively filed by trial and error until obtaining the code component that allows opening with a filing different from the original one. The identified code component is the code component of the master key for the position in which the code component is located. By repeating such operation for the other positions of the code components, it is possible to retrieve the entire code of the master key.